I am looking to actuate a 12V SPDT relay depending on weather or not a 12V PWM signal is received or not. Headlamps use a reduced power PWM signal for daytime running lamps. I want to be able to detect that signal separate from a 12VDC source (normal headlamp operation) and actuate a relay based on it to relocate that daytime running lamp to another location. I am an ME by trait but have limited experiences with circuits.
I have been able to use a simple RC circuit to turn that PWM into a lower constant voltage. Trouble is, I don't know how to compare the full 12V and the reduced voltage and also still carry enough amperage to control a relay coil.
Looking for something as simple as possible. Some have suggested using a using a 555 as a retrig monostable missing pulse detector or an RC circuit with a comparator. I don't know if either of these would work or how to specifically design them. Any help would be greatly appreciated!